docs: def eval(self, key, default=None, loc=None, correct_key=True):
          """Evaluates and sets the specified option value in
          environment `loc`. Many options need ``N`` to be defined in
          `loc`, some need `popsize`.
  
          Details
          -------
          Keys that contain 'filename' are not evaluated.
          For `loc` is None, the self-dict is used as environment
  
          :See: `evalall()`, `__call__`
  
          """
          # TODO: try: loc['dim'] = loc['N'] etc
          if correct_key:
              # in_key = key  # for debugging only
              key = self.corrected_key(key)
          self[key] = self(key, default, loc)
          return self[key]